1. Field of the Invention
The present invention relates to a method of measuring the height of burres and a burr height measuring head for carrying out the same and, more particularly, to a method of measuring the height of burres formed in the clamping portion of a crimp-style terminal (hereinafter referred to simply as "terminal") in swaging or crimping the clamping portion of the terminal and a burr height measuring head for carrying out the same.
2. Description of the Prior Art
Generally, a cable is fastened to a terminal by swaging or crimping portion of the terminal as shown in FIG. 7. In fastening a cable to a brass terminal, the bared end W of the cable is placed in the U-shaped clamping portion 21 of the terminal placed on the lower die 23 of a terminal crimping machine, and then the side walls of the U-shaped clamping portion is crimped so that the extremities 21a of the side walls are bent inward to clamp the bared end W of the cable with the U-shaped clamping portion 21 as shown in FIG. 5. In some cases, burres 25 are formed in the crimped clamping portion 24 thus formed as shown in FIG. 6.
Flashes 25 occur in a gap 26 between the mating faces of the upper die 22 and the lower die 23. Therefore, the size of burres 25 increases gradually as the gap 26 between the mating surfaces of the upper die 22 and the lower die 23 increases due to the enlargement of the die opening 22a of the upper die 22 or the abrasion of the mating edges 23a of the lower die 23 when the upper die 22 and the lower die 23 are used on the terminal crimping machine for a long time.
Such a burr 25 reduces the clamping force of the terminal, deteriorates the electrical and fastening characteristics of the crimped clamping portion 24, and also stress 27 is concentrated near the burr 25 as shown in FIG. 6 so that, in the worst case, a crack is formed near the burr 25 and the crimped clamping portion 24 breaks off. Furthermore, the burres 25 interfere with a connector housing in inserting the terminal into the connector housing, making the inserting operation quite dilfficult.
Accordingly, it has been an ordinary practice to control the quality of the crimping process by directly measuring the height of the burr from time to time with a vernier caliper, by indirectly measuring the height by forming an image of the crimped clamping portion by an optical projecting system or by measuring the height by a contour tracer.
However, it is difficult to measure the height directly at a sufficient accuracy with a vernier caliper because the height of the burr is very small. In measuring the height of the burr by an optical projecting system, the terminal fastened to a cable by crimping must be cut off from the cable to form the image of the burr by the optical projecting system, resulting in a time-consuming operation. Although capable of measuring the height of the burr at a high accuracy, the contour tracer is very expensive and hence it is impossible to provide a terminal crimping line with many contour tracers for efficient measurement.